Stamper rounds out automation suite with rigid transfer
Throughput gain leans on rigidity
Stamping manufacturer A.J. Rose, Avon, Ohio, supplies precision-formed, deep drawn, metal products and assemblies such as transmission pistons, torque converter components, impellers, engine timing rings, ABS, water pump components, accessory drive pulleys, AC compressor clutch components, and numerous other powertrain components. The stamper needed the transfer system for a new transfer press to be robust and rigid to minimize tooling bar deflection and vibration. In addition, the system had to be compatible with existing tooling and to integrate well with a servo press’s variable speeds and modes
When you’re a contract stamping manufacturer, your “product” is your set of capabilities.
“Our product really is our tool design and our process,” said Dan Pritchard, CEO and president of A.J. Rose Manufacturing Co., a supplier of precision-formed, deep-drawn metal products and assemblies such as transmission pistons, torque converter components, impellers, engine timing rings, ABS, water pump components, accessory drive pulleys, AC compressor clutch components and numerous other powertrain and suspension components (see Figure 1). Parts from 21⁄2 to 14 in. diameter are stamped from stainless steel; aluminum; high-strength, low-alloy (HSLA); and hot-rolled steel on both progressive-die and transfer presses.
“Customers come to us with their biggest problems, and we solve them,” Pritchard said.
Those problems include the need for weight reductions, cost reductions, and increasingly more complicated parts.
“What’s happened in the last couple of years is that people will come to us with a two-piece welded or riveted assembly and want us to convert it to a one-piece stamping,” Pritchard said. More complex components often call for a longer die set and longer press bed or transfer press capabilities.
Another challenge the company has faced is converting a cast or machined part to a metal stamping (see Figure 2). “I might walk the assembly line with customers, look at what they’re currently manufacturing or assembling, and say, ‘Hey, that looks like it’s a candidate for conversion to a stamping.’”
Weight reductions often are obtained by stamping today’s advanced high-strength steels. This may require using more die stations (again, requiring a longer press bed) or using a servo press’s restrike capabilities to counter springback.
Pritchard wanted to increase A.J. Rose’s capacity and throughput to meet those customer demands and to position the company to be able to continue to solve customer problems and challenges. He determined that the company could do that with a new transfer press system.
The company installed a 700-ton AIDA servo transfer press with a Wayne Trail through-the-window servo transfer system.
Transfer System Requirements: Rigidity, Productivity, Compatibility
Like any manufacturer facing ever-increasing cost pressures, A.J. Rose expected the system to facilitate increased throughput. To do so, the company needed a robust, rigid transfer system to minimize tooling bar deflection and vibration, Pritchard said. In addition, A.J. Rose already had other transfer press systems and so the new system had to be compatible with existing tooling. It also had to integrate well with a servo press’s variable speeds and modes.
Rigidity, Productivity. A.J. Rose’s objectives to increase throughput and speed required that the transfer system minimize vibration and tooling deflection.
“We were looking for more stability because our presses and bed lengths are getting longer,” Pritchard said. “If you get deflection or vibration at higher rates of speed, you’re going to lose control of a part, potentially crash, and damage the die tooling—not to mention throughput losses.”
Another reason for the need for increased rigidity is that some of the parts must be flipped between stations to be formed from opposite directions, Pritchard said.
“You have to control the part. Being able to control that part during that flipping process—being able to time when it starts and complete the flipping process so that it’s not running into the next station—is huge.
“And it gets pretty delicate,” Pritchard continued. “One, you have to time the flipping. Two, you don’t want to create a larger pitch between stations and then have to build a longer and more expensive tool just because you’ve got dead space to flip the part before it goes to the following station.
“So we asked, ‘How can we pick up stability?’”
Tooling Bar Compatibility. The new transfer system had to be compatible with A.J. Rose’s existing transfer tooling bars and systems. The stamper wanted to be able to run it in any of its presses.
The stamper has operated 3-axis servo transfers for 25 years and is on its third transfer builder. Pritchard estimated that three dozen existing tooling bars are already on-site.
The existing tooling bars were custom-designed for the existing transfer systems. Two 220-in.-long bars move out of the end of the window of the press. “I bet we’re one of the few people that run the full-length bar, rather than segmented bars,” Pritchard said.
Pritchard added, “That compatibility was major. That was probably the one big requirement that I said we absolutely had to have, because we weren’t going to start retooling finger bars for all of our jobs, and then marrying them to certain presses, where we wouldn’t have interchangeability.
“We really are married to a certain size transfer bar now. To go larger than that is going to put us out of our window. So we needed to pick strength and rigidity, but working within that same envelope.”
Sync With Servo Press. Finally, like any transfer system outfitted into a servo press, the new transfer was tasked with having to synchronize with the press’s variable speeds and motion profiles.
How the System Works
Wayne Trail Vice President of Sales Doug Knapke explained how the unit is constructed to reduce deflection and vibration, thereby allowing the servo press to operate at higher speeds.
The drivetrain design incorporates precision-ground helical rack-and-pinion gears in all three axes. The helical gears provide maximum tooth contact, resulting in minimal backlash and enhancing accuracy and repeatability.
An added benefit is the elimination of many moving parts and mechanical linkages associated with belt drives and ball screws, providing a simpler and easier-to-maintain system.
The drivetrain design played a role in minimizing deflection; however, in addition, the transfer carriage design, transfer guidance system, and the manner in which the bars are coupled to the transfer carriage assemblies also contribute significantly to rigidity.
The transfer system’s front and rear tooling bars attach to two carriage assemblies (see Figure 3). The carriage assemblies support those tooling bars from end to end and inward as much as possible. That is critical in supporting the bars completely to minimize deflection and vibration that would otherwise occur in the center of the tooling bar, according to Knapke.
He said, “Collaborating with A.J. Rose’s engineers, the challenge for us was coming up with a custom design for connecting those existing tooling bars to our system without compromising system integrity and stability.”
Pritchard and his engineers had collaborated with Wayne Trail on adapting the system. “When we were in the design planning, I was concerned about where the bar was supported, because we were moving the connection of the four points. We were moving the pinpoint even further out on a transfer that’s mounted on the outside of the upright.
“So in discussions with Doug and his group, we said, let’s cantilever the design so that the mechanics that operate the motions are all outside, bolted to the upright, but then we’re cantilevering the rails support all the way in, through the upright window,” Pritchard said (see Figure 4).
Results: Rigidity Increases Productivity 15 Percent
A.J. Rose’s throughput increased by 15 percent with the new transfer system, Pritchard said. “So we’re picking up about 15 percent in strokes per minute because of this rigidity that we have now. And that’s been huge.
“We’re sold on the rack-and-pinion design,” Pritchard said. “The rigidity, the construction of the unit with the helical gear rack and pinion is leaps and bounds above what we were getting.
“The way the bar is designed to attach to the transfer system gives it more contact length. Whereas in prior designs, our engagement point would only be 4 inches on the linear bearings at the four corners and pinned at the end for the pitch drive, and that was it,” Pritchard said.
“That 15 percent throughput increase is directly related to the transfer system.”
Durability. The company experienced a side benefit of the all-helical rack-and-pinion drive design: The elimination of mechanical linkages reduces the number of moving parts to maintain and minimizes the risk of component failure.
“We already have a lot of belt drive equipment, which leads to another major point we considered—the durability of the unit,” Pritchard said. “Because of the increased rigidity, it’s not beating itself to death. It holds up to the speeds, the environment we put it through. We’re not constantly replacing bearings, stretched belts.
“We’ve had it for two years now, and I don’t think we’ve bought a service part for it yet. Our guys love not having to work on it,” he added.
Serviceability. Pritchard said that being able to service the system easily was on the wish list. “We wanted a complete transfer unit on the exterior of the press for ease of serviceability.
“On a lot of the older style units, the mechanical boxes that provide the lift and the grip motion are between the end of the bolster and the upright of the press. So we used to have to order presses with an extra 3 in. of length on each side to house these boxes. That was definitely one of the things we wanted to eliminate.
“So not only did we solve the problem with rigidity, productivity, and serviceability with the design change, the construction, and the bar support, now we have 6 more inches of bed space.”
So Happy Together
Tooling Compatibility. “Now I can take just about any tool we’ve got and run it in five different machines,” Pritchard said. “We’re using the same bars, but the way they’re fastened and married to the transfer unit itself via the transfer design promotes the rigidity and stability.”
Servo Press Synchronization. Wayne Trail, collaborating with A.J. Rose engineers, developed software that allows the transfer system to run safely and reliably with the press in any of the numerous profiles the servo press can operate, Knapke said. “We’ve developed our software in a manner to be able to basically follow the press in any mode that it can run without introducing additional unwanted motions.”
Pritchard added, “Wayne Trail’s ability to sync with the different types of slide motion–specifically the rapid restrike motion—was critical.”
Pritchard is happy with the results. “It’s a great example of increased productivity and better capital utilization so that we can offset all of the other costs that are going up,” he said.
Is he happy enough with the results to do it again? A.J. Rose just installed a new 1,200-ton Minster transfer press and near-twin Wayne Trail servo transfer system in March.
STAMPING Journal is the only industrial publication dedicated solely to serving the needs of the metal stamping market. In 1987 the American Metal Stamping Association broadened its horizons and renamed itself and its publication, known then as Metal Stamping.